The population distributions of the Zanbil adakitic dacites
were modeled by mixing together two populations of crystals with linear CSDs, termed fine grains and phenocrysts, for both amphibole and plagioclase.
Barker (ed.), Trondjemites, dacites
and related Rocks, Elsevier, Amsterdam: 1-12.
Porphyritic andesite to dacite
lava flows (Lava Dacttica Apilulco; thickness < 4 m) with planar fracturing subparallel to the surface constitute the main effusive products.
Trachytes have more K-feldspar than plagioclase and biotite and no quartz compared to dacites
. Plagioclase phenocrysts show oscillatory to patchy zoning.
Firstly, the rocks of the NW part of the Iberian Chain have more evolved compositions (basalts to dacites
), higher degrees of alteration (Table 2) and no peridotite xenoliths.
The Pliocene volcanics are generally dominated by andesites, whereas dacites
occur as dominant phase in Pleistocene volcanics.
Verma (1999) reported that andesites and dacites
from the Sierra de Chichinautzin volcanic field (central MVB) were derived from partial melting of a heterogeneous mafic granulite from the lower crust.
The geologic history of this deposit begins with the intrusion of stocks of tonalitic composition (the Andacollo porphyry, Upper Cretacous) within a layered sequence of andesite and dacites
, which induced pervasive hydrothermal alteration (K silicate, quartz sericite) and mineralization (mainly pyrite-chalcopyrite plus some minor quantities of molybdenite, bornite, cubanite and pyrrhotite).
The metaconglomerate is poorly deformed and contains cm-size pebbles of sandstones, pelites, cherts, limestones, plutonic rocks (quartz-diorites, tonalites and granitoids) and volcanic rocks (basalts, andesites, dacites
and glass fragments).